Preheat the oven to 400°F (200°C). Place the bones on a baking sheet and roast for 20-30 minutes until golden brown.

Transfer the roasted bones to a large stockpot or slow cooker. Add the carrots, celery, onion, apple cider vinegar, bay leaves, thyme, parsley, and peppercorns.

Pour in enough water to cover the bones and ingredients.

Bring to a gentle boil, then reduce to a low simmer. Cover and cook for 12-24 hours. If using a slow cooker, set it to low and let it cook undisturbed.

Once done, strain the broth through a fine-mesh strainer into a large bowl to remove bones and solids.

Allow the broth to cool completely before transferring it to airtight containers. Store in the refrigerator for up to 5 days or freeze for up to 6 months.